Extent of heavy metals pollution and health risk assessment of groundwater in a densely populated industrial area, Lagos, Nigeria

Exposure to heavy metals pollutions in water predisposes consumers to human and environmental health deterioration. In this study, the extent of heavy metals contamination, water quality index, ecological and human health risk assessments of groundwater resources in Ajao industrial area of Lagos, Nigeria were carried out. Results revealed that Cu is the most prevalent heavy metal, contaminating 85.71% of the analyzed water samples. Based on the groundwater quality index, 76.19% of the samples are of excellent water quality and suitable for drinking, domestic and industrial purposes. However, the quality of 23.81% variedly deteriorated. Ecological risk assessment revealed that 85.71% and 14.29% of the samples pose low and moderate ecological risks, respectively. This assessment also showed that Cu was the major heavy metal posing ecological risk in the industrial area. Based on hazard quotients, Cu impacted the potentiality of chronic diseases than other heavy metals. Health hazard index analysis revealed that children are more exposed to non-carcinogenic chronic health risks due to ingestion of contaminated groundwater than the adult population. Probability of cancer risk (PCR) revealed that 19.05% of the samples pose high Cr cancer risk for both adult and children, while 14.29% pose high Cd and Ni cancer risks. Correlation and factor analyses indicated that the origin of the heavy metals in water is majorly attributed to anthropogenic inputs rather than natural, geogenic processes. Awareness programs towards protecting the groundwater in this area should be launched and encouraged. Moreover, contaminated water should be treated before use.